As electronic organ circuitry continues to become more sophisticated, the practice of encoding a portion of a keyboard to a binary word has become quite common. Such encoding is done at high speed, with keys being scanned under the control of a clock running at a rate of up to 150 kilohertz, for example.
The binary word thus developed, or the data corresponding thereto, such as a pulse in a predetermined time slot, can be used for many purposes. Automatic chords, automatic sounding of note patterns, or automatic sounding of bass notes are a few examples of the use of the data which such an encoded word forms, or develops.
A problem associated with the actuation of automatic circuits of the nature referred to by encoded words is that of the mechanical key bounce associated with key switches actuated by the keys of a keyboard. Contact bounce of such key switches can cause false triggering of automatic circuits by supplying false data thereof and must, therefore, be counteracted or eliminated to obtain proper circuit operation.
A simple method of counteracting key bounce is to provide a delay in the acceptance of each new binary word from the keyboard encoder. However, a problem is presented in selecting an optimal delay time. Further complicating the problem is the fact that, while keyboards are manufactured within certain tolerance limits, every keyboard will have differences between the amount of bounce of one key as compared to that of another key.
If keyboard delays are set to compensate for the worst case of difference between keys, the keyboard operation will become sluggish. However, if keyboard delay is decreased to speed up operation, false signals created by key bounce will become a problem.
It is an object of the present invention to develop an improved keyboard delay circuit to eliminate the effects of key bounce.
It is a further object of the present invention to provide a keyboard delay circuit to prevent the development of false data by eliminating key bounce and which is inexpensive to manufacture and is inherently integrable in substantially any circuit through the present state of the art of semiconductor circuits.